1. Field of the Invention
The present invention relates to a process for producing highly stretchable amorphous anisotropic melt-forming polymers suitable for use in the production of a variety of shaped articles including films, fibers, and blow molded forms. This invention also relates to the polymers produced from the subject process, as well as to shaped articles, such as multilayer laminates and bicomponent fibers, made from the polymers.
2. Description of the Prior Art
Anisotropic melt-forming polymers, also known as liquid crystalline polymers or "LCPs", are well known in the art. Anisotropic melt-forming polymers exhibit a parallel ordering of molecular chains in the melt phase and are also termed "thermotropic" liquid crystal polymers. Many of these materials are wholly aromatic in nature.
Thermotropic polymers include aromatic copolyesters having recurring units derived from p-hydroxybenzoic acid, at least one aromatic diol and at least one aromatic dicarboxylic acid as well as wholly aromatic copolyesteramides having recurring units derived from p-hydroxybenzoic acid, at least one aromatic diol, at least one aromatic diacid, and aminophenol. Without the inclusion of recurring units that disrupt the crystalline structure, such polymers tend to have very high melting points, for example, 360.degree. C. and above, making them difficult to melt fabricate. Incorporation of recurring units that provide non-parallel or "kinky" linkages is a common means of lowering melting point. These kinky linkages include "meta" or 1,3-aromatic ring structures.
Common materials from which meta linkages are derived include m-hydroxybenzoic acid, isophthalic acid, resorcinol, and m-aminophenol. U.S. Pat. Nos. 4,563,508; 5,037,939; and 5,066,767 disclose polymers containing recurring units derived from p-hydroxybenzoic acid, terephthalic acid, isophthalic acid, hydroquinone and 4,4'-biphenol; U.S. Pat. No. 4,912,193 discloses polymers having recurring units derived from p-hydroxybenzoic acid, 4,4'-biphenol, terephthalic acid and isophthalic acid; U.S. Pat. No. 4,966,956 discloses polymers having recurring units derived from p-hydroxybenzoic acid, terephthalic acid, isophthalic acid, 4,4'-biphenol and aminophenol; U.S. Pat. No. 5,663,276 discloses polymers having recurring units derived from p-hydroxybenzoic acid, terephthalic acid, 4,4'-biphenol, isophthalic acid, hydroquinone and 4,4'-biphenyldicarboxylic acid; U.S. Pat. No. 5,089,594 discloses polymers having recurring units derived from p-hydroxybenzoic acid, terephthalic acid, isophthalic acid, 4,4'-biphenol, and an aromatic diol, for example, hydroquinone; U.S. Pat. No. 4,722,993 discloses polymers having recurring units derived from m-aminophenol, p-hydroxybenzoic acid, terephthalic and/or isophthalic acid, one or more of hydroquinone, 4,4'-biphenol or resorcinol and, if desired, m-hydroxybenzoic acid; U.S. Pat. No. 5,399,656 discloses polymers having recurring units derived from p-hydroxybenzoic acid, terephthalic acid, resorcinol and an aromatic diol, for example, 4,4'-biphenol; U.S. Pat. No. 5,025,082, discloses polymers having recurring units derived from p-hydroxybenzoic acid, terephthalic acid, 4,4'-biphenol, 2,6-naphthalene dicarboxylic acid, and at least one aromatic diol selected from hydroquinone, methylhydroquinone, trimethylhydroquinone, resorcinol and tetramethylbiphenol; and U.S. Pat. No. 5,798,432 discloses polymers having requiring units derived from p-hydroxy benzoic acid, 2,6-naphthalene dicarboxylic acid, terephthalic acid, isophthalic acid, hydroquinone, p-aminophenol and 4,4'-biphenol.
The presence of meta linkages notwithstanding, aromatic polymers derived from p-hydroxybenzoic acid, at least one aromatic dicarboxylic acid and at least one aromatic diol and/or aminophenol tend to have highly ordered crystalline structures and, although drawable in the melt, generally lack the ability to be stretched to a significant degree at temperatures below the molten state.
Another class of thermotropic polymers has recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, at least one aromatic diacid and at least one aromatic diol. The incorporation of meta linkages into such polymers is described, for example, in the following: U.S. Pat. No. 4,522,974 disclosing polymers having recurring units derived from p-hydroxy benzoic acid, 6-hydroxy-2-naphthoic acid, hydroquinone and isophthalic and/or terephthalic acid; U.S. Pat. No. 4,920,197 disclosing polymers having recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, isophthalic acid and resorcinol; U.S. Pat. No. 4,937,310 disclosing polymers having recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, isophthalic acid and resorcinol; U.S. Pat. No. 4,918,154 disclosing polymers having recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic and/or isophthalic acid, resorcinol and hydroquinone; and U.S. Pat. No. 4,983,713 disclosing polymers having recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 4,4'-biphenol, and isophthalic acid. The polymers set forth in the examples of these patents tend to have ordered crystalline structures and are not considered to be highly stretchable materials.
More recent patents disclose liquid crystalline polymers that include amorphous materials. Example 5 of U.S. Pat. No. 5,525,700 is directed to what appears to be an amorphous polymer having recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, hydroquinone, terephthalic acid, 4,4'-biphenol and 2,6-naphthalene dicarboxylic acid. Crystalline polymers derived from the same recurring units are also disclosed. In fact, of the numerous polymers exemplified by this patent, all but Example 5 are crystalline materials. Example 5 is not believed to be a highly stretchable polymer.
U.S. Pat. No. 5,656,714 discloses amorphous and what are termed "semi-crystalline" polymers having recurring units derived from p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, terephthalic acid, 4,4'-biphenol, and resorcinol. Fibers made from the amorphous polymers of Examples I and IX were respectively reported to be drawn to 73 and 30 times their as-spun length. Apart from Examples I and IX, no additional data regarding the stretchability of the exemplified polymers is provided. The polymers exemplified by U.S. Pat. No. 5,656,714 vary in terms of their degree of crystallinity; some, but not all, of these polymers are highly stretchable.
LCPs that are stretchable at lower temperatures have a diverse range of end-use applications. Amorphous LCPs having a Tg (i.e., onset of the glass transition temperature as measured by differential scanning calorimetry or "DSC") of 150.degree. C. or less that are highly stretchable at temperatures above Tg, but below the temperature at which the LCP is in the molten state, are of particular interest in the production of articles that are stretched, drawn or otherwise processed at lower temperatures. Liquid crystalline polymers that are stretchable at temperatures below the processing temperatures of conventional film-forming polymers such as, for example, polyolefins or polyalkene terephthalates, for example, PBT or PET, may be particularly desirable for use in the production of multilayer articles such as films, laminates, blow-molded containers, and the like. In these multi-layer applications, the barrier, mechanical and/or optical properties of liquid crystalline polymers may provide advantages that are typically not obtained from conventional thermoplastics. EP 0 928 683 A2, published Jul. 14, 1999, discloses a variety of multi-layer laminates, including laminates formed from wholly aromatic, liquid crystalline polymers of the type disclosed in U.S. Pat. No. 5,656,714.
A process for producing highly stretchable amorphous LCPs and the LCPs so produced are desired.